In manufacturing semiconductor electronic components, an important step consists in treating a semiconductor substrate in a controlled atmosphere at very low pressure, e.g. for depositing layers of various materials by plasma deposition.
In industrial production, substrates in the form of wafers are conditioned and brought successively into a process chamber through an airlock or through a transfer chamber. In the process chamber, the atmosphere must be controlled very accurately, in particular to avoid the presence of any impurity or of any pollution.
Progress made in recent years in the semiconductor industry is essentially related to the increase in the integration of electronic circuits into components of a few square millimeters in area, defined on silicon wafers that are increasingly large.
Numerous (up to 400) technological steps are required to make such circuits, and, during the process, the pressure in the process chamber is subjected to sudden variations between various steps during which the pressure must be controlled and set to appropriate values.
Generating the low-pressure controlled-atmosphere in the process chamber requires the use of effective pumping systems. Such a system generally comprises a primary pump whose outlet is connected to atmosphere and whose inlet is connected to the outlet of a secondary pump such as a turbomolecular pump whose inlet is connected to the process chamber.
The process steps in the process chamber require the presence of special gases, and, by acting on the substrate, they generate gaseous compounds that must be removed. As a result, the pumping system must pump a variable atmosphere containing gaseous compounds that must be treated by gas treatment apparatus in order to deliver to atmosphere only compounds that are inoffensive.
Currently, pumping and gas treatment systems are situated remote from process chambers, i.e. they are connected to process chambers via long and costly pipes that are over ten meters long.
The reason behind that distance and those pipes is that current pumping and gas treatment systems are heavy and voluminous, and they give rise to adverse effects such as vibrations that it is essential to avoid in the process chamber.
Currently, an electronic component factory is therefore designed in a building having at least two levels, the upper level containing the process chamber(s), and the lower level containing the pumping and gas treatment apparatus. Pipes interconnect the two levels to convey the vacuum.
The pipes which are essential in known structures suffer from several drawbacks:
the pipes themselves generate vibrations; PA1 the pipes constitute a large surface area on which the pumped gases can deposit in the form of particles; particles deposited in that way can backscatter from the pipe into the process chamber, thereby increasing the contamination of the chamber during subsequent steps of the process; PA1 the pipes require major mechanical support means; PA1 to reduce the deposits in the pipes, it is possible to provide temperature control, but such control is extremely costly and very difficult to implement; PA1 a monitoring and control system that is complex to implement must be provided for reasons of safety in the event of leakage, since the pumped gases are harmful; and PA1 the considerable amount of space needed requires large facilities and large floor areas for the factories; their cost is very high; losses from the cold line are non-negligible. PA1 the gases are pumped out from the process chamber by means of a primary pump and of at least one secondary pump; PA1 the pumping speed is adjusted so as to maintain the pressure adapted to each treatment step in the process chamber; PA1 the extracted gases are analyzed upstream from the primary pump; and PA1 the result of the analysis of the extracted gases is used to adjust the pumping speed as a function of the pumped gases, so as to determine the variation in the pressure inside the process chamber during the stages of the treatment. PA1 treating the gases downstream from the primary pump; and PA1 analyzing the gases at the outlet of the primary pump so as to determine their nature and their state and so as to adapt the pumping parameters, constituted by the temperature of the primary pump, the injection of dilution gas into the primary pump, and the speed of the primary pump, in order to optimize the effectiveness of their treatment. PA1 a pumping line comprising said primary pump constituted by a variable-speed dry primary pump, and at least one secondary pump mounted upstream from said primary pump; PA1 speed control means for controlling the speed of the primary pump; PA1 first gas analyzer means suitable for analyzing the extracted gases upstream from the primary pump, and for producing first gas analysis signals; and PA1 first signal processing means for producing a speed control signal as a function of said first gas analysis signals, and for transmitting said speed control signal to the control means for controlling the primary pump. PA1 downstream from the primary pump, gas treatment means for treating the extracted gases; PA1 at the outlet of the primary pump, second gas analyzer means determining the nature and the state of the pumped gases and producing second gas analysis signals; and PA1 second signal processing means for producing second speed control signals for controlling the speed of the primary pump as a function of the second gas analysis signals, which second control signals can be sent to the power supply apparatus of the primary pump.